prestonian

Looking for a little help.
My a/c stopped blowing cold all of a sudden.
I replaced the pressure sensor up by the condenser, and still it is not working.
Upon looking at the compressor, the clutch is always spinning even when I shut down the entire climate control system.
From best I can tell, the compressor clutch should not be engaged while the AC system is off.
The compressor is spinning freely, not seized or anything.
Any suggestion on what to look for next?
If it is the compressor itself, damn that thing is down there tight.
BTW, my car is a 2012 3.0T with 80K.

Thanks.

Mesquite77

Start with the easy stuff:

1) On most cars, the clutch is triggered by a relay, which can go bad and stick on. This will also flatten your battery pretty quick. Search youtube for "sticking clutch relay"
1.1) If clutch always engaged, then pressure probably has gone to high at some point and refrigerant blew out of relieve valve, you should have heard that, or seen "smoke" from under hood (actually oil mist)
2) Scan for codes, these cars are plenty smart...
3) Check refrigerant pressure on low port, clutch engages until pressure get high enough to shut-off, though I agree if A/C is off this likely not the problem

prestonian

Thanks for the reply.
I pulled codes on an obd2 reader but nothing.
I didn't have a chance to hear any pressure relief valve let go. Had to run inside a store while my son was in the car with AC on. When I came back, it was not working.
He swears he didn't touch anything. Lol
Will research the clutch relay...anyone have a diagram to its location?

Mesquite77

There are 2 DTC codes for magnetic clutch shorts. Are you using a VW, VAG scanner like VCDS or OBDeleven? $15 scanner will not read VW specific controller DTCs.

I'm not expert at wiring diagrams, but it appears as if the Audi J255 controller, directly controls the A/C clutch without a relay. The controller is part of the A/C dash display. Replacing it is not for the faint of heart...

prestonian

I have a standard obd2 reader. Not a VW/Audi VAGCOM. So yes, it is limited.
Will likely just bring car in to my local guy.
This car is way more advanced than my other cars including my 93 urS4.

Jworkx

Last time I hade Issue with my A/C last summer. Well it was still blowing cold air but once in awhile compressor makes a weird whining noise and its pretty much close to being a little annoying especially when your at a stop. Went to the dealer and found out that some A/C compressors from the Q5 are really known issue for A/C clutch or pretty much failing.. good thing they replaced mine with the new revised part.. under warranty. Mines is 2017 Audi Q5 2.0T and has 45,xxx kms when it got replaced

Cyclone1078

Hey Prestonian,
I have the exact problem, same model, engine, even the same mileage 88K. I have a 00256 code for a pressure sensor but i think thats just collateral damage.
I also have codes U111300 & B11D501 (which could be from a previous repair) as well. The compressor shouldn't be engaged with the controls off. I'm thinking
the clutch is locked up. Did you require a compressor?
Thanks
Cyclone1078

LaAudi12

I have a a6 2012 3.0t an the same problem just happens to me a week ago but I haven’t tried changing the a/c compressor sensor yet. I have a feeling I have the same issue as you. Can you please tell me if you found out the problem

Cyclone1078

The problem with mine was the pressure sensor below the plastic radiator shroud. I scanned it and the code pointed to the sensor. Very easy fix. I found one on Ebay that appears to be OEM for a little over $20. Its been working fine now for a couple weeks. No need to purge the freon there's a valve under the switch. The compressor does rotate at all times which is different than most others i've serviced.